Author a free body diagram question

A free body diagram question requires students to draw forces from one or more starting points (called control points) on top of a background image.

A sample free body diagram question is shown including the student instructional banner.

IMPORTANT: Free body diagram questions don't support algorithms.

TIP: All questions are authored using the Question Editor. Check out Author a question to learn how to access the Question Editor.

To author a free body diagram question

To author a free body diagram question from the Question Editor:

  1. Enter the question statement in the Question Text pane of the Question Editor.

TIP: Check out Use the Visual Editor for details on how to use this toolbar to the fullest to control the visual appearance of your free body diagram question text.

  1. Click Response Areato select the type of response area for this part of the question.

NOTE: A question can have multiple question parts. Each question part can have a different type of response area. Example — A question could have the first response area as a free-body diagram response area, and a second response area as multiple choice.

  1.  Click Free Body Diagram from the list of response area types.

  1.  Assign a weight to the response area. The default response area weighting is 1.

TIP: The response area weight can be any integer greater than 0. Response area weighting is proportionate to the question total. Example — A question with two response areas could have the first response area weighted as 2, and the second response area weighted as 4. This means that the second response area will be worth twice as much as the first response area when calculating the total grade for the question.

  1. Define the allowed angle tolerance for the student's drawn forces. The default angle tolerance is 5.0°.

NOTE: Angle tolerance is measured in degrees and means that the student's drawn force can be ±n compared to the correct response, where n is the defined angle tolerance.

  1. Click Browse to select the background image for the forces to be drawn on.

  1. Navigate within the Class File Manager to the image file that you want to use. Double click on the image file that you want to insert as the free body diagram background image.

NOTE: The image that you select is uploaded into your question from the Class File Manager. If the image you want to use isn't stored in your Class File Manager, you can click Upload to make the desired image available in your Class File Manager for use in your question.

Check out Manage folders in the Class File Manager to learn about storing and managing supplementary content.

NOTE: The maximum image file size is defined by your organization's Möbius administrator.

NOTE: Your uploaded image will be scaled down (with the aspect ratio preserved) to fit the drawing board if you upload a background image with a width exceeding 600 pixels or a height exceeding 450 pixels.

  1. Select whether the free body diagram instructional banner will be displayed that guides the student on how to use the free body diagram drawing board. The default selection is No (the instructional banner isn't displayed by default).

NOTE: The instructional banner appears as follows for your students:

The instructional banner displays in an orange box and reads: Start drawing forces by clicking on a starting point and dragging your cursor to the desired area or make a selction below and click Draw.

You can instead define your own set of free body diagram drawing board instructions in your question text if you choose to not use the pre-built Möbius instructional banner.

  1. Select the check boxes of the forces that you want to include as options in your response area from the Select forces pane. The forces that you select are the forces that will appear as options to the student when they're drawing their free body diagram response.

TIP: You can select to include forces in addition to the required forces to act as distractor options for your students.

TIP: You can also define your own force to include in the response area:

  1.  Define the abbreviation for the force in the Abbr. field.

  1. Define the full name of the force in the Name field.

  1.  Click Add force type to add your custom force to the list of available forces.

  1.  Select the check box of your custom force that has been added to the list of available forces.

  1. Resume at step 10 of To author a free body diagram question.

  1.  Click Update force selection list below to add the selected forces to the list of options that will be available to the student when they're drawing their free body diagram response.

  1. Define the control point label and then click Add. Control points are where your force angles originate.

TIP: You can have more than one control point.

TIP: Modify your control point label as needed and click Update Label to update your control point label.

TIP: Click Delete to erase your control point from both the free body diagram and list of available control points.

  1. Your control point is automatically inserted on top of your background image. These control points are visible to your students while they're drawing their forces and can't be edited by your students.

TIP: Click-and-drag your control point at any time to relocate it to anywhere on the background image.

  1. Select a force from the Choose a Type drop-down list. The forces that you selected in step 9 are the options that are available in the drop-down list.

  1.  Define an angle (in degrees) for the force with respect to the control point.

NOTE: Valid angles are between -180° and 360°, inclusive. Half angles are also accepted (Example100.5°).

TIP: Multiple forces can be drawn from a single control point.

TIP: If you have more than one control point, use the Origin drop-down list to define which control point the force will use as its starting point.

  1.  Click Draw.

IMPORTANT: The forces and control points that you're drawing signify the correct response(s). A student must duplicate your entries (within the angle tolerance) to get the question correct.

  1. The force is added to the free body diagram at your defined angle.

TIP: Click-and-drag a force's handle to redefine its angle and length as needed.

NOTE: Arrow length is disregarded for grading since force magnitudes aren't considered.

  1. Draw and edit control points and forces as needed to create your perfect free body diagram.

TIP: The hamburger menu supports your drawing and editing of forces with the functions of:

  • Creating a new force on the diagram using your defined force options and control points.
  • Selecting a force that's already been drawn.
  • Clearing all forces (after confirmation) from the drawing board.

TIP: Select a drawn force on the drawing board (or using the hamburger menu) and click Delete to remove it from your free body diagram.

  1. Click Insert to add this response area to the question.

  1. The response area is inserted into your question.

  1. Click Preview to trial your new question to ensure that it behaves as expected.

TIP: You first have to click the save iconif you're creating this question from within an Activity Editor. After the question has been saved, you can then click the preview iconto ensure that your new question behaves as expected.

  1. Click Save to save your new question. Your new question is now stored in the Questions pane of the Content Repository.

TIP: Click the save iconif you're creating this question from within an Activity Editor. This saves your question to the activity and the Content Repository.

Grading details for free body diagram questions

Free body diagram questions are graded automatically by Möbius.

Students are graded on their ability to:

  • Draw the correct type of force
  • Use the correct number of forces
  • Use the correct control point(s)
  • Draw the correct angle(s)

Partial grades aren't awarded.

The angle tolerance acts as a question-wide tolerance, but you can also override this tolerance by customizing how angles are matched on a per-force basis.

Customize angle matching

Customizing angle matching overrides the question-wide angle tolerance (described in step 5 of To author a free body diagram question).

You can use three options for each force answer:

  • default — Specifies to use a question-wide tolerance on the angles (default value is 5.0°).
  • collinear — Ensures that the student’s forces lie along the same line as the correct answer force, within the question-wide angle tolerance (Example — If the correct answer is with a question-wide tolerance of , a collinear response of 177° to 183° will be accepted using the collinear angle matching option).
  • any — Matches the name of any student force against the name of the correct answer force, regardless of the angle.

To customize angle matching:

  1.  Navigate to the question’s Content Summary pane in the Content Repository.

  1. Click Edit Source from the Edit menu.

  1. Complete the angleCriteria field by specifying default, collinear, or any.

TIP: You can use the options of default, collinear, or any.

Example — Suppose the correct answer consists of three forces: a default angle matching for the first, collinear for the second, and any for the third. This would be specified as:

angleCriteria = ["default", "collinear", "any"]@

TIP: You can alternatively supply your own Maple comparison procedure rather than stating collinear or any. This procedure must accept exactly three input arguments: two angle values in the range from 0 to 360, followed by a non-negative tolerance value. It must return either true (meaning that the angles are considered equivalent) or false.

Example — A procedure can check if two angles are in the same quadrant:

proc(a1, a2, tol) evalb(a1>=-tol and a2>=-tol and a1<=90+tol and a2<=90+tol or a1>=90-tol and a2>=90-tol and a1<=180+tol and a2<=180+tol or a1>=180-tol and a2>=180-tol and a1<=270+tol and a2<=270+tol or a1>=270-tol and a2>=270-tol); end proc

Maple will replace the third argument with the question’s angle tolerance value.

  1. Click Save & Close to return to the Content Repository.